Installation guide

8 IBM Eserver xSeries 366 Technical Introduction
– Web servers
–E-mail
Note that Microsoft® licensing of the Windows 2000 Server operating systems is by
number of processors (four-way for Server, eight-way for Advanced Server, 32-way for
Datacenter Server). Therefore, the appearance of twice as many logical processors can
potentially affect the installation of the operating system.
Windows Server 2003 understands the concept of physical processors versus logical
processors. For more information about Hyper-Threading, see the following Web sites:
http://www.intel.com/technology/hyperthread/
http://www.microsoft.com/windows2000/server/evaluation/performance/reports/hype
rthread.asp
򐂰 Extended Memory 64 Technology (EM64T)
First introduced in the Xeon DP “Nocona” processor, EM64T is a 64-bit extension to the
industry standard IA32 32-bit architecture. EM64T adds:
– A set of new 64-bit general purpose registers (GPR)
– 64-bit instruction pointers
– The ability to process data in 64-bit chunks
Even though the names of these extensions suggest that the improvements are simply in
memory addressability, Intel EM64T is in fact a fully functional 64-bit processor.
To reap the full benefit of this technology, you need to have a 64-bit operating system and
64-bit applications that have been recompiled to take full advantage of this architecture.
Existing 32-bit applications running on a 64-bit operating system can also benefit from
EM64T.
The “Cranford” processor limits memory addressibility to 36 bits of addressing.
There are three distinct operation modes available in EM64T:
– 32-bit legacy mode
The first and, in the near future, probably most widely used mode will be the 32-bit
legacy mode. In this mode, EM64T processors will act just like any other IA32
compatible processor. You can install your 32-bit operating system on such a system
and run 32-bit applications, but you will not be able to make use of the new features
such as the flat memory addressing above 4 GB or the additional General Purpose
Registers (GPRs). 32-bit applications will run just as fast as they would on any current
32-bit processor.
Most of the time, IA32 applications will run even faster because of numerous other
improvements that boost performance regardless of the maximum address size.
– Compatibility mode
The second mode supported by EM64T is the compatibility mode, which is an
intermediate mode of the full 64-bit mode described below. To run in compatibility
mode, you will need to install a 64-bit operating system and 64-bit drivers. If a 64-bit
OS and drivers are installed, the processor will be enabled to support both 32-bit
applications and 64-bit applications.
The compatibility mode gives you the ability to run a 64-bit operating system while still
being able to run unmodified 32-bit applications. Each 32-bit application will still be
limited to a maximum of 4 GB of physical memory. However, the 4 GB limit is now
imposed on a per-process level, not on a system-wide level. This means that every
Tip: For all intents and purposes, Intel EM64T and AMD AMD64 are identical.